iMac 2.93 Core 2 Duo / 10.6.8 I have a continuing issue with the screen freezing up in the middle of random activities at random times but it feels like once you get into something for about half an hour or so it happens most. Only option is to hold button down and restart. I thought it was the wireless mouse and keyboard because, oddly, the pointer still move after a freeze but nothing was selectable. I put the wired keyboard and mouse back on and thought that fixed it but the problem is back and the mouse does not move in a freeze. The thing that is most odd was the random patterning seen on the screen... it sort of jumbled around like one of those sliding square puzzles ... lines, pixilation, full panels of graphics shuffling... sometimes just plain frozen with no fun effects. Anyone hear about this and know how to fix? Thanks!